Coupling connectors are currently used to connect adjacent segments of plastic pipe, especially for pipes having substantial diameters.
These connectors are substantially constituted by a collar, which surrounds the end regions of a pair of mutually aligned thermoplastic pipes.
An electric resistor is inserted in the inner part of the connector.
By passing electric current through said resistor, the end portions of the pipes are fused together.
Experience and practice in the field have shown that to provide an optimum joint it is necessary to clean the ends of the pipes to be welded before applying the connector.
Cleaning the ends relates to eliminating mud, moisture and sand, but also to removing the layer of oxide that inevitably forms on the outer surface of plastic pipes.
Originally, the end parts of the pipes to be joined were generally cleaned by hand.
However, this manual cleaning entailed several drawbacks, including the one related to the fact that a human operator had to assess arbitrarily the amount of material that he was removing, and such an assessment is extremely difficult to perform on site.
Moreover, manual elimination of the material was never uniform and could case imbalances that had a negative effect on the successful outcome of the welding.
Moreover, manual removal was time-consuming and ultimately expensive in terms of work time.
In order to avoid these drawbacks, a plurality of devices have been devised which are suitable to eliminate, in a substantially semiautomatic or automatic manner, a layer of material and therefore to prepare the end part of the pipes to be welded.
One of these apparatuses is disclosed in EP-0740974 in the name of the same Applicant/Inventor.
This apparatus comprises anchoring means, which are fixed, in the active configuration, to the end region of the pipe, and to which a threaded pivot is coupled so that it can perform a longitudinal rotary and translational motion; said pivot is arranged axially with respect to the pipe, and supporting means for a tool that can be positioned so as to interfere with, and remove material from, the outer surface of the end portion of the pipe, are coupled to said pivot so that they rotate monolithically therewith.
The anchoring means comprise a substantially cylindrical element, which is shaped at one end so as to form a circumferential slot and is shaped at the other end so as to form radial guides for elements for anchoring to the pipe.
The supporting means comprise a first telescopic rod-like arm, which is fixed radially by means of one of its ends to the free end of said threaded pivot, and a second rod-like arm, which is fixed by means of one of its ends to the free end of said first arm and supports the tool.
Although this apparatus achieves its task and improves substantially work quality and times with respect to manual preparation, it has been found susceptible of improvements.
Such apparatus in fact has limited functionality in relation to the diameters of the pipes that can be worked, due to the dimensional constraints between the substantially cylindrical element and the radial guides (the diameter of the former limits the maximum length of the radial guides and therefore the maximum pipe diameter to which anchoring is possible).
The Applicant subsequently devised a new apparatus, which is disclosed in EPA-02020520.9.
This apparatus comprises anchoring means that are fixed, in the active configuration, to the end portion of the pipe and to which a threaded pivot (arranged coaxially to the axis of the pipe) is coupled so that it can perform a longitudinal rotary and translational motion; supporting means for at least one tool, which can be arranged so as to interfere with, and remove material from, the outer surface of the end region of the pipe, are rigidly coupled to said pivot so that they rotate monolithically therewith.
The anchoring means comprise an annular retention element for first ends of centrally-pivoted lever systems, which are at least partially radial and angularly equidistant and support, so that they are articulated at second ends substantially in a rocker-like configuration, elements for resting against the inside wall of a pipe.
The retention element can perform an adjustable translational motion on a tubular supporting element, with which said threaded pivot engages internally; a disk protrudes from said supporting element, and said lever systems are pivoted thereto and therefore are articulated in order to change their inclination with respect to the axis and keep said supporting elements pushed against said pipe wall.
This apparatus also, however, can be improved; said apparatus is in fact excessively heavy, and this makes it difficult to handle and apply to the pipes and entails a constructive complexity that affects production costs.
In construction yard practice, moreover, there is often the need to replace portions of already-installed damaged pipelines.
The repair procedure generally consists in removing the portion of damaged pipeline; then, after performing the appropriate cleaning and scraping operations,two electroweldable sleeves are applied by fitting them over their entire length on the two ends of the pipes formed after removing the damaged portion. A new pipe segment is then inserted to replace the damaged portion, and the two sleeves are then subjected to a translational motion so that they adhere to the existing pipe over half of their length and to the new pipe over the other half. Welding is then performed.
Clearly, the region to be scraped that relates to the pipes of the old pipeline must be equal to the total length of the sleeves that are to be applied, in order to allow the sliding of the sleeve on the existing pipe during full insertion.
Currently known apparatuses do not allow great flexibility in the distance of the scraping from the end section of the pipe; the companies that manufacture these apparatuses in fact generally prepare different models depending on the possible welding distance and pipe diameters.